1. Field of the Invention
The invention relates to location information services provided in association with a communication system, and in particular to communication of information when providing information about a location of a mobile user equipment visiting a network other than a home network.
2. Description of the Related Art
Various services can be provided for a user of a mobile user equipment by means of a communication system. Recent development in the field of mobile user equipment has lead to arrangements wherein information about the location of a mobile user equipment is determined and utilized when providing services for the user equipment or other parties. Such services are sometimes called location sensitive services.
A mobile user equipment may comprise, for example, a mobile telephone, a laptop computer, a personal data assistant or any other mobile station enabled for wireless communication with another station. An example of a communication system providing mobility for users thereof is the public land line mobile network (PLMN) or cellular network. Another example is a mobile communication system that is based, at least partially, on use of communication satellites. Wireless communications may also be provided by means of other arrangements, such as by means of local wireless area networks.
The skilled person is aware of the basic principles of a wireless communication system. A wireless communication system typically operates in accordance with a given standard or specification which sets out what the various elements of the system are permitted to do and how that should be achieved. For example, the standard or specification may define if the user, or more precisely, user equipment or terminal is provided with a circuit switched service or a packet switched service or both. Communication protocols and/or parameters which shall be used for the connection are also typically defined. For example, the manner how communication shall be implemented between the user equipment and the elements of the communication network is typically based on a predefined communication protocol. In other words, a specific set of “rules” on which the communication can be based on needs to be defined to enable communication by means of the communication system.
A communication system needs to be able to provide various different functions in order be able to operate. These functions can be divided in different categories. A category comprises functions that relate to the actual carrying of communications such as voice or multimedia or other data content in the system. Another category can be seen as being formed by control or management functions such as the control of various services and the actual communication. Signaling associated with different functions is thus understood as being carried on different planes. For example, control messages are communicated on a control plane and the actual communication is transported on a user plane. The communication on the user plane is supported the signaling of the control messages on the control plane. The predefined rules commonly dictate the appropriate plane that shall be used for communication.
Typically the communication systems provide the different planes by means of separate channels, e.g. by means of separated signaling and communication channels. Such arrangements are employed e.g. by signaling system 7 (SS7) core networks and Q.931/GSM/WCDMA subscriber access. Therefore the term signaling channel may be used when referring to control plane communications. Similarly the term communication channel may be used when referring to user plane communications.
The various functions of communication systems may have developed quite independently from each other. Different protocols may also be used in different communication systems. The standards and protocols define e.g. which plane shall be used for a certain purpose.
The mobile network apparatus and/or user equipment can be employed for provision of information regarding the geographical location of the user equipment and thus the user thereof. A mobile user equipment and thus the user thereof can be positioned by various different techniques. For example, substantially accurate geographical location information that associates with a user equipment can be obtained based on a satellite based positioning system, for example the GPS (Global Positioning System) or Galileo. More accurate location information can be obtained through a differential GPS or an assisted GPS (A-GPS). In an approach the cells or similar geographically limited radio access entities and associated controllers of the communication system are utilized in production of an estimate concerning the location of a mobile user equipment. To improve the accuracy of the location information the communication system may be provided with additional equipment, for example specific location measurement units (LMUs), that provide more accurate data or additional data that may be used when locating of a user equipment.
It is also possible to conclude information about the geographical location of a user equipment when the user equipment is located outside a home network thereof, i.e. when the user equipment is located in a coverage area of a visited or “foreign” network. The visited network may be made capable of transmitting the location of the mobile user equipment back to the home network, e.g. to support services that are based on location information or for the purposes of routing and charging.
Location information may be used for various purposes, such as for location of a mobile telephone that has made an emergency call, for locating vehicles or given mobile subscribers for commercial purposes and so on. In general, a client (for example a user or another entity wishing to receive location information regarding a user may) may send a request for location information to the location service provision entity. An appropriate location service entity will then process the request, obtain the required data and generate an appropriate response.
Communication associated with location services may be signaled on the control plane and/or user plane, the selection depending on the application.
Applications that use control plane for communication of at least a part of information for location determination commonly employ embedded signaling protocols. Communications that associate with location information services may be communicated solely on the control plane. However, this may cause relatively high load on the control plane. This may be especially the case on the air interface between a mobile user equipment and a radio network servicing the mobile user equipment.
It has been proposed that a mobile user equipment could be located by using user plane signaling for communication of at least a part of location service information. Some of user plane applications are a kind of overlay solutions wherein a data connection is established on a user plane between a relevant server and a mobile user equipment to transfer on radio interface information that is needed in location determinations. The user plane data connection may be especially established for communication of location information. In another approach location information may be communicated on a user plane connection established for other purposes. The user plane signaling may be based on appropriate communication protocol, for example the Internet Protocol (IP) or data messages such as short message service messages. An example of the proposals presented in Open Mobile Alliance (OMA) wherein user plane is used is known by the work name ‘Secure User Plane Location’ (SUPL).
In practice a user plane location system requires that the mobile user equipment knows an address or other routing information for a user plane location server so that the mobile user equipment can exchange information with the server on the user plane. A user plane location server may also need to know the identity, such as the Mobile Subscriber Integrated Services Digital Number (MSISDN) or other identifier, of the mobile user equipment or other routing information in order to form a user plane connection to the mobile user equipment.
The proposal is believed to work satisfactorily when the user is in his/hers home network. However, problems may arise when a user is roaming in other networks. A roaming mobile user equipment may not know the address or other identity information related to the local user plane enabled location service entity, for example a local SUPL server. If a user equipment knows only the address of the home network location service entity, a problem is that the home network location service entity may not be able to provide assistance data relevant and valid in the roamed network. If a mobile station gets a location request from a user plane enabled location service entity while roaming, the user equipment may need to be able to trust that the location service entity is a legitimate entity allowed to request location information and to send assistance data.
As a more detailed example of the possible problems, lets consider a situation where a user who is a subscriber to a Finnish cellular network roams in a cellular network in the USA. The mobile user equipment of the user is not aware of the IP address of the local server, for example a local SUPL server, of the roamed network in the USA. The local server may nevertheless need the location of the roaming user equipment, for example in order to be able to provide the location of the roaming user equipment for emergency services. In the case of an emergency call the local server of the roamed network may try to request location information from the mobile user equipment, but the mobile user equipment does not know whether it can trust the origin of the request or not. Furthermore, if the mobile user equipment wants to get assistance data, it is possible in certain applications that the user equipment may only know the user plane address of a location service server in the home network in Finland. The home network server, however, may not have all assistance data that is needed for location in the USA.